#!/usr/bin/env python

import argparse
import os
import sys
import math

from scapy.all import *

if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Plot two PCAP files')
    parser.add_argument('--client', metavar='<pcap file name>', help='pcap file to parse', required=True)
    parser.add_argument('--server', metavar='<pcap file name>', help='pcap file to parse', required=True)
    args = parser.parse_args()
    
    if not os.path.isfile(args.server):
        print('"{}" does not exist'.format(args.server), file=sys.stderr)
        sys.exit(-1)
    if not os.path.isfile(args.client):
        print('"{}" does not exist'.format(args.client), file=sys.stderr)
        sys.exit(-1)

    # calc owd
    packets_send = rdpcap(args.client)
    packets_rec = rdpcap(args.server)
    
    # check len
    PACKAGES = 4000
    if (not len(packets_send) >= PACKAGES) or (not len(packets_rec) >= PACKAGES):
        print("Nicht genug Pakete!")
        exit()
        
    owds = []
    for i in range(0, PACKAGES):
        owd = packets_rec[i].time - packets_send[i].time
        owds.append(owd)
        
    mittwelwert = sum(owds) / len(owds)
    varianz = 0
    for owd in owds:
        varianz = varianz + (owd - mittwelwert)**2
    varianz = varianz / len(owds)
    stdabw = math.sqrt(varianz)
    
    print("Mittelwert: " + str(mittwelwert))
    print("Varianz: " + str(varianz))
    print("Standardabweichung: " + str(stdabw))